1. Field
The invention relates to devices having rotors operating inside housings to provide expanding and contracting chambers.
2. State of the Art
Various rotary compressors, pumps expansion devices have been proposed in the art, wherein the rotor is an irregular cylinder angularly symmetrical about its axis of rotation. The rotors are mounted within the housing to rotate eccentrically with respect to the shaft of the device, which is concentric with the housing. Typically, the rotor and shaft are constrained into fixed rotational relationship by a pair of eccentric meshing gears, one fixed to the rotary member and the other to the crankshaft. See. U.S. Pat. No. 4,156,586, FIG. 1, for example. Use of gears in this manner stems from the use of epitrochoidal or hypotrochoidal surfaces for the basic shape of the rotor, or the housing, the housing being the envelope of the rotor in the former case and the rotor being the envelope of the housing in the latter. Use of gears in this manner is so well known that it is apparently considered as part and parcel of these types of rotary devices, and need not even be claimed, their presence being felt to be implicit. See also U.S. Pat. No. 4,012,180, FIG. 7 and column 3, lines 26 et seq, as another example. The use of such gearing pairs is of course expensive, and desirably avoided if possible.
Another typical problem with prior art rotary pumping devices and the like, is that the chambers produced by the basic trochoidal shape with its envelope produces chambers which, although varying in volume with rotation of the rotor, do not reduce to zero. The volummetric compressive efficiencies of such devices leave something to be desired.
Another disadvantage that accrues from use of the basic trochoidal shapes is that the envelope is swept out by the apexes of the rotor and seals must be provided at these angular tips. In some instances the tips have been rounded to provide for substantial sized seals. However, this has lead to the necessity for the seals to travel radially to the rotor as its positions changes within the housing. Many solutions have been proposed for this seal problem, but, to the knowledge to the present inventor, none are entirely satisfactory. See U.S. Pat. Nos. 4,043,714, 4,012,180 and 4,018,548 for examples.
Another disadvantage of many prior art rotary displacement devices is the necessity to provide check valves and the like on inlet and outlet fluid passages through the housing, to prevent discharged fluids, compressible or incompressible as the case may be, from flowing back into the device after the discharge passage of the rotor.
Clearly, a need exists for a rotary displacement device, whether used for expansion or compression of compressible fluids, or pumping of incompressible fluids, that has improved volummetric efficiency, reduced or non-existent seal problems between the rotor and the housing, which needs no phasing gears nor check valves installed in the inlet and outlet passages. Further, there exists a need for a rotary pumping device wherein the inlet and/or outlet flow rates are constant rather than pulsating as with present devices.